Proportioning pumps are utilized to deliver a primary fluid, such as water, to livestock, crops or other applications. Typically, the proportioning pump introduces a metered amount of additive liquid, e.g. chlorine, fertilizer or other chemicals, into the primary fluid. Representative proportioning pumps are disclosed, for example, in U.S. Pat. Nos. 5,055,008 and 5,234,322.
Proportioning pumps of the prior art do not exhibit optimal efficiency. During operation of the pump, a pressure differential is created on opposite sides of the pump's main driving piston. This pressure differential holds the pump valves closed against their respective valve seats. Accordingly, known proportioning valves employ an overcenter linkage and attached spring mechanism that overcomes the pressure differential by lifting the valves from their respective seals and causing them to reverse position as the piston translates within the pump. In instances where the primary fluid is flowing rapidly and the pressure differential is great, a substantial spring tension is usually required to operate the valves. However, the pressure differential and spring tension tend to oppose one another. The stronger the tension spring that is used, the greater will be the pressure differential needed to operate the spring. This differential must be sufficiently great to drive the piston, pump additive fluid, overcome friction and overcome the force of the tension spring acting on the valves. Accordingly, in many cases the fluid flow and pressure differential must be increased to operate the tension spring and overcenter linkage. This is undesirable in applications where a less forceful fluid flow is required. Unfortunately, most known proportioning pumps still tend to employ large, relatively inefficient tension springs and pressure differentials.
Known proportioning pumps also continue to exhibit problems with tension spring failure. When the spring breaks or otherwise fails, the valves can no longer reverse position and the piston will cease pumping. This can have disastrous consequences for livestock or crops. The above-referenced patents disclose various systems which continue to provide primary fluid in the event of spring failure. However, those systems employ mechanisms, such as bypass valves and pivoting linkages, that are themselves potentially subject to failure. A simpler, more reliable failsafe system for insuring uninterrupted fluid flow is required.
The typically high pressure differential employed by most proportioning pumps can also create problems with the secondary piston that is used to pump the additive fluid into the primary fluid. This piston is typically enclosed in an additive pump body that is attached to the main pump body. High fluid pressures within the pump body can cause the extension to be inadvertently dislodged. In particular, if a person using the pump attempts to remove the additive pump body when the device is under high pressure, the additive pump body may suddenly or violently separate from the main body and present the risk of injury to that person.
Many types of machines, in addition to proportioning pumps, employ a reciprocating piston engine to drive the mechanism. Conventional engines driven by volatile fossil fuels are energy inefficient and present a risk of explosion.